Disposal of low- and intermediate-level waste in Switzerland: Basic aspects of potential relevance to microbial effects

Summary Current projects for the disposal of low-and intermediate-level radioactive waste in Switzerland are based on the concept of a horizontally accessed repository under a hillside. Most of the waste to be disposed of in such a repository is operational and decommissioning waste from nuclear power plants and wastes from medicine, industry and research. This waste is generally solidified in cement and placed in steel drums or concrete containers. Once the by the anaerobic corrosion of steel and by microbial degradation of organic material, to escape from the near field. Valanginian marl, which is one of three envisaged options for the host rock, is characterized by a high carbonate content, up to 75% in some locations. The organic content of the marl is between 1% and 2%, while pyrite is present in concentrations up to 5%. The groundwater is reducing, and its pH tends to lie in the neutral to slightly alkaline range. Potentially important microbial effects on the long-term performance of the system are microbial degradation of barrier materials and organics, the effect of microorganisms on sorption, and their role as catalysts.     

Purification from human plasma of endogenous dodium transport inhibitor(s)

Summary Na⁺, K⁺-ATPase inhibitors extracted from plasma of healthy human subjects displaced³H-ouabain binding to human erythrocytes and inhibited the Na⁺ efflux catalyzed by the Na⁺, K⁺-pump and unexpectedly the Na⁺, K⁺-cotransport system without alteration of the Na⁺, Na⁺-exchange or the Na⁺ passive permeability. This suggests the presence in healthy human plasma of endogenous factors with ouabain-like and furosemide-like activities.Acknowledgments. We are indebted to Dr M. A. Devynck for her advice on chemical measurements and to Dr R. P. Garay for his help with flux measurements     

Zinc ions block the second but not the first phasic response to repetitive application of carbachol and histamine in guinea-pig taenia caeci

In the presence of Zn²⁺ (0.3 mM), carbachol (10^–6 M) or histamine (10^–5 M) induced the phasic response in guinea-pig taenia caeci while the tonic response was markedly inhibited. However, when the muscles were kept in Zn²⁺-containing medium following the first stimulation with either carbachol or histamine, neither application of carbachol nor of histamine elicited another phasic contraction. Caffeine (25 mM) did not induce contraction in the presence of Zn²⁺. After the washing out of caffeine in the presence of Zn²⁺, however, the muscle did then develop the phasic response on the application of carbachol or histamine. In conclusion, Zn²⁺ did not affect the carbachol or histamine-induced Ca²⁺ release from the storage sites. However, when Zn²⁺ was continuously present, Ca²⁺ was not supplied to the storage sites. Furthermore, carbachol and histamine mobilized a common cellular Ca²⁺ store, but they activated Ca²⁺ release channels different from the ones activated by caffeine in the Ca²⁺ storage sites.     

Lack of Na+,K+-ATPase expression in intercalated cells may be compensated by Na+-ATPase: A study on MDCK – C11 cells

The lack of Na⁺,K⁺-ATPase expression in intercalated cells (IC) is an intriguing condition due to its fundamental role in cellular homeostasis. In order to better understand this question we compared the activities of Na⁺,K⁺-ATPase and Na⁺-ATPase in two MDCK cell clones: the C11, with IC characteristics, and the C7, with principal cells (PC) characteristics. The Na⁺,K⁺-ATPase activity found in C11 cells is far lower than in C7 cells and the expression of its β-subunit is similar in both cells. On the other hand, a subset of C11 without α-subunit expression has been found. In C11 cells the Na⁺-ATPase activity is higher than that of the Na⁺,K⁺-ATPase, and it is increased by medium alkalinization, suggesting that it could account for the cellular Na⁺-homeostasis. Although further studies are necessary for a better understanding of these findings, the presence of Na⁺-ATPase may explain the adequate survival of cells that lack Na⁺,K⁺-ATPase. Received 09 July 2008; received after revision 03 August 2008; accepted 12 August 2008     

Role of calcium in the histamine release induced by D-galactosamine from rat mast cells

Summary Rat peritoneal mast cells were isolated and purified by differential centrifugation in Ficoll. Cells pooled from three to four rats were suspended at approximately 10⁶ cells/ml in a buffered salt solution and incubated for 1 h at 37°C in 300 l volumes in the absence or presence (9×10^–4 M) of calcium chloride. Addition of D-galactosamine hydrochloride (DGM; 2.8×10^–4 M) caused (in addition to basal release) a mean ±SEM percent histamine release of 15.7±5.2 in the presence of Ca⁺⁺ and 19±4.9 in the absence of Ca⁺⁺ (p>0.05). It is suggested that D-galactosamine does not require extracellular Ca⁺⁺ for the release of histamine from the rat mast cell.A preliminary analysis of these results was presented at the International Symposium on calcium entry blockers and tissue protection, Rome, 15–16 March 1984.     

DNA synthesis in the nuclei of differentiating muscle fibers of the silkworm,Bombyx mori L.

Summary Incorporation of³H-thymidine (³HTdr) into the nuclei of myofibril-containing myofibers of larvae of the silkworm,Bombyx mori, was shown by means of light microscope (LM) and electron-microscope (EM) autoradiography. The number of DNA-synthesizing myonuclei attains 42% 12–18 h after each molt. Thus in the developing silkworm DNA replication and myofibrillogenesis are coexisting and not mutually exclusive processes as is the rule in vertebrate somatic myogenesis.     

Modelling of microbial degradation processes: The behaviour ofmicroorganisms in a waste repository

Summary In a repository for radioactive disposal the waste material is kept in place by several shells and boundaries to prevent a long term recycling of the material into the environment. Present investigations on various chemical and biological processes can be extrapolated into future centuries only with great uncertainty. Models may therefore be a good tool to forecast processes which may occur within the repository and to estimate whether the barriers present will prevent the leaching of waste material within a given time span. A mathematical model is described based on an experimental laboratory setup, a microcosm described by West et al.^19–22 simulating in a laboratory system repository conditions for a Swiss L/ILW repository. It includes microbial as well as physico-chemical processes. These simulations indicate that biological processes such as gas formation or proton release should also be included into the safety assessment of the repositories.     

Consideration of microbiology in modelling the near field of a L/ILW repository

Summary The long-term safety of proposed repositories for nuclear waste is demonstrated by the use of chains of mathematical models describing the performance of the various barriers to radionuclide mobilisation, transport, release into the biosphere and eventual uptake by man. Microbial contamination of such repositories is to be expected, and hence the extent and consequences of microbial activity must also be quantified. This paper describes a modelling approach to determine the maximum microbial activity in the near field of a repository, which can thus be related to maximum possible degradation of performance. The approach is illustrated by application to a proposed Swiss repository for low- and intermediate-level waste (L/ILW), which is immobilised in concrete and emplaced in a marl host rock.     

Effect of xanthurenic acid on P-450-dependent biotransformation by molting glands in vitro

Incubation of molting glands from the crayfishProcambarus clarkii (Y-organ) and the silkwormBombyx mori (prothoracic gland) with 23,24-[²H₄]-2-deoxyecdysone resulted in the production of deutero-ecdysone; this biotransformation was inhibited in the presence of xanthurenic acid. When the experiments were performed under an¹⁸O₂ atmosphere, the¹⁸O atom was introduced into ecdysone, as confirmed by mass spectrometry. We therefore suggest that xanthurenic acid inhibits P-450-dependent hydroxylation of 2-deoxyecdysone. However, deutero-2-deoxyecdysone was not converted to 3-dehydroecdysone when using Y-organs in vitro, although it is a major product. We therefore conclude that the biosynthetic pathway of ecdysteroids inP. clarkii branches at an early step.     

42K spaces in submandibular gland of early postnatal rats: effects of carbachol and transport inhibitors

Summary Equivalent spaces of⁴²K were measured in fragments of the submandibular gland of 1-, 7-, 14- and 21-day-old and adult rats in the absence and presence of carbachol and the transport inhibitors ouabain and furosemide. The results indicate that the⁴²K space was increased by carbachol in an ouabain-sensitive manner at all ages studied and that part of the secretagogue-stimulated K uptake occurred by way of a furosemide-sensitive transport system in the latter part of the postnatal period and in the adult.     

Displacement activity of some natural cularine alkaloids at striatal3H-SCH 23 390 and3H-raclopride binding sites

Five natural cularines isolated from the aerial parts ofSarcocapnos crassifolia (Fumariaceae) and a cularioid isolated from the bark ofGuatteria ouregou (Annonaceae) were tested for their ability to displace³H-SCH 23 390 and³H-raclopride from their striatal binding sites. Celtisine, breoganine and cularidine were able to inhibit the binding at D-1 and D-2 dopaminergic sites at nanomolar concentrations. Other alkaloids were active at micromolar concentrations. These data suggest that the presence of an oxepine system in the isoquinoline skeleton could lead to compounds which would be very active and possibly selective at dopaminergic receptor sites.     

Chromate reduction inStreptomyces

Summary Streptomyces species 3M grew in peptone yeast extract medium with 1000 g/ml K₂Cr₂O₇. Incubation of the chromate with different cell fractions in the presence of NADH and NADPH resulted in a decrease of Cr⁶⁺ in the reaction mixture. The level of Cr⁶⁺ was reduced by 82.7% by a particulate cell fraction obtained by centrifugation at 105,000×g for 1 h, in the presence of NADH. The reducing enzyme was associated with this cell fraction. The enzyme was constitutive and reduced Cr⁶⁺ to Cr³⁺.     

Microbiology of subteranean waste sites

Summary Excavated repositories for radioactive waste in deep and shallow geological formations will be subject to microbial contamination; therefore, a number of groundwater environments have been examined in Europe for the presence and activity of microorganisms. Common soil bacterial isolates were found to predominate in the groundwaters. Their activity is curtailed by the oligotrophic conditions encountered. It still remains to be demonstrated whether waste and waste isolation materials such as cellulose and bitumen will provide an exogenous nutrient source for the microorganisms and whether microbial activity will compromise nuclear waste immobilisation. A further constraint to the microorganisms is the high pH near-field environment generated by cement/concrete barriers.     

Phospholipid composition of cardiac (Na++K+)-ATPases from various species

Summary There is a difference in phospholipid composition of cardiac (Na⁺+K⁺)-ATPase preparations between species which are sensitive to ouabain and those which are not. Sphingomyelin is higher and phosphatidylcholine is lower in the enzymes from sensitive species than in those from insensitive ones. Lysophosphatidylcholine is detectable only in the latter preparations.     

Magnesium enhances human pancreatic elastase digestion of125I-labeled elastin

Summary The effect of some divalent cations, especially Mg⁺⁺, on elastinolysis by porcine or human pancreatic elastase has been determined using¹²⁵Iodine-labeled elastin as substrate. Elastin degradation was significantly increased in the presence of 10^–3 M Mg⁺⁺. If elastin was pre-incubated with 0.5 (w/v) Triton, there was a further increase in elastinolysis to 2.6 times the original rate.     

Studies of total and protein-bound plasma Mg++ in wild and hatchery-reared coho salmon smolts in freshwater and in seawater

Summary Total plasma Mg⁺⁺ and Ca⁺⁺, Mg⁺⁺ in erythrocytes as well as protein-bound plasma Mg⁺⁺ were investigated in wild and hatchery-reared smolts. The proportion of plasma Mg⁺⁺ which was bound to plasma protein did not change significantly during entry into seawater, even though the in vitro addition of exogenous Mg⁺⁺ to the plasma showed that additional binding was possible.     

Sulfhydryl oxidation induces calcium release from fragmented sarcoplasmic reticulum even in the presence of glutathione

Alcian blue and plumbagin induced transient Ca²⁺ release from fragmented sarcoplasmic reticulum. Dithiothreitol (DTT) and glutathione (GSH) partially blocked Ca²⁺ release induced by these oxidizing compounds. Pretreatment of alcian blue and plumbagin with DTT or GSH for more than 1 min was required to abolish the ability of the oxidizing compounds to release Ca²⁺. Mg²⁺ and ruthenium red completely blocked alcian blue-and plumbagin-induced Ca²⁺ release. These results suggest that oxidation of sulfhydryls on Ca²⁺ release channels induces Ca²⁺ release even in the presence of GSH in situ.     

Influence of ethanol on calcium,inositol phospholipids and intracellular signalling mechanisms

Summary Studies have implicated Ca⁺⁺ in the actions of ethanol at many biochemical levels. Calcium as a major intracellular messenger in the central nervous system is involved in many processes, including protein phosphorylation enzyme activation and secretion of hormones and neurotransmitters. The control of intracellular calcium, therefore, represents a major step by which neuronal cells regulate their activities. The present review focuses on three primary areas which influence intracellular calcium levels; voltage-dependent Ca⁺⁺ channels, receptor-mediated inositol phospholipid hydrolysis, and Ca⁺⁺/Mg⁺⁺-ATPase, the high affinity membrane Ca⁺⁺ pump.Current research suggests that a subtype of the voltage-dependent Ca⁺⁺ channel, the dihydropyridine-sensitive Ca⁺⁺ channel, is uniquely sensitive to acute and chronic ethanol treatment. Acute exposure inhibits, while chronic ethanol exposure increases⁴⁵Ca⁺⁺-influx and [³H]dihydropyridine receptor binding sites. In addition, acute and chronic exposure to ethanol inhibits, then increases Ca⁺⁺/Mg⁺⁺-ATPase activity in neuronal membranes. Changes in Ca⁺⁺ channel and Ca⁺⁺/Mg⁺⁺-ATPase activity following chronic ethanol may occur as an adaptation process to increase Ca⁺⁺ availability for intracellular processes. Since receptor-dependent inositol phospholipid hydrolysis is enhanced after chronic ethanol treatment, subsequent activation of protein kinase-C may also be involved in the adaptation process and may indicate increased coupling for receptor-dependent changes in Ca⁺⁺/Mg⁺⁺-ATPase activity.The increased sensitivity of three Ca⁺⁺-dependent processes suggest that adaptation to chronic ethanol exposure may involve coupling of one or more of these processes to receptor-mediated events.     

The effect of a phorbol ester upon the cholinergic regulation of potassium permeability in the rat submandibular gland

Acetylcholine releases calcium from cytoplasmic stores and permits an influx of calcium in salivary acinar cells. The resultant rise in [Ca²⁺]_i causes an increase in potassium permeability which is an important part of the secretory response. We have investigated the effects of 12-0-tetradecanoyl phorbol-13-acetate, a potent activator of protein kinase C, upon this regulation of potassium permeability in superfused pieces of rat submandibular salivary gland. This compound inhibited the initial [Ca²⁺]_o-independent component of the response of acetylcholine but had no effect upon the subsequent [Ca²⁺]_o-dependent phase. This compound does not, therefore, appear to inhibit receptor-regulated calcium influx.     

The effect of cyclic AMP on Na+ and K+ transport systems in mouse macrophages

Summary Exogenous cyclic AMP (cAMP) inhibits the Na⁺, K⁺-cotransport system and stimulates the Na⁺, K⁺-pump and Na⁺, Ca²⁺ exchange in mouse macrophages. These effects are enhanced by inhibition of phosphodiesterase with methylisobutylxanthine (MIX). MIX alone showed little or no effect. A similar response was observed after stimulation of endogenous production of cAMP by isoproterenol.